Conventional coil components include a coil component described in U.S. Pat. No. 6,362,986. This coil component has a core with an open magnetic circuit structure, a primary-side coil wound around the core, and a secondary-side coil wound around the core and magnetically coupled to the primary-side coil. The inner magnetic path of the primary-side coil and the inner magnetic path of the secondary-side coil are arranged on the same straight line or are arranged on non-collinear straight lines.